Serous carcinoma. With & without chemo?

My mother was diagnosed with serous carcinoma, high grade. She has gone through hysterectomy with b/l salpingo oophorectomy. She also was given adjuvant radiotherapy (IGRT technique, 50 Gy in 25 fractions and 3 applications of HDR brachytherapy total dose of 15 Gy). Now the doctor has suggested Chemotherapy for 3-4 sessions in 21 day intervals. However, he also mentioned that there is no proven study for the effectiveness of chemo for patients with Stage 1a high grade serous carcinoma. Can you guide us on following: - is Chemo necessary for such patients? - given that she is 61 yrs and has a history of big illnesses every year (dengue, chikungunya, eye infection that couldn't be diagnosed for 6 months etc), how likely is it that chemo will weaken her permanently after the treatment? - have seen cases where chemo lead to relapse of severe leukaemia. So which is better: No chemo vs Chemo with side effects - what is the recurrence rate of such cancers with & without chemo? Many thanks.